This invention relates to a disk rotating apparatus for reliably rotating a magnetic disk accommodated in e.g. a floppy disk assembly.
Floppy disk assemblies accommodating a magnetic disk having a diameter of 3.5 inches have recently come into use as the memory media in word processors and personal computers. The floppy disk assembly is inserted in the housing of the word processor or the like, in which state the magnetic disk accommodated therein is driven rotatively by a rotating apparatus. When the disk is being rotated, an operation is performed for writing information onto the magnetic recording surface of the disk or for reading information from the recording surface.
In a disk rotating apparatus according to the prior art, the magnetic disk which has been inserted in the word processor or personal computer housing is chucked as shown in FIG. 1A. The first step of this chucking operation is to attract, by a magnet provided on the top side of a spindle hub, not shown, a disk hub a made of metal and integrally supporting the magnetic disk. The disk hub a is provided with a center hole b, in which a spindle shaft c is inserted, and a drive hole d. As shown in FIG. 1B, a drive pin e, which is supported by a pin holding member upwardly biasing the lower end of the pin, is inserted in the drive hole d.
In this conventional disk rotating apparatus, the spindle shaft c is pressed against a specific corner portion of the center hole b in disk hub a to position the magnetic disk with respect to the spindle shaft c. This is done by utilizing the reaction force of the drive pin e produced when the drive pin e is brought into abutting contact with a corner portion of the drive hole d at rotation of the magnetic disk.
If the drive pin e should happen to shift in the direction indicated by the arrow X in FIG. 1C due to e.g. a fluctuation in the torque of the magnetic disk, the positional relationship between the drive pin e and drive hole d will change. As a result, there will be a decline in the positional accuracy of the spindle shaft c relative to the center hole b, thereby causing an off-track phenomenon. In an attempt to prevent this from occurring, the conventional disk rotating apparatus axially supports the pin holding member, which holds the drive pin e, on the spindle hub so as to be capable of turning back and forth horizontally by a prescribed amount, and includes a torsion coil spring which biases the pin holding member horizontally in a prescribed direction. However, adopting this expedient increases the number of component parts and makes assembly troublesome.
In order to solve the aforementioned problems, a proposed arrangement disclosed in the specification of Japanese Utility Model Application Laid-Open (KOKAI) No. 61-16747 has a spring member f (see FIG. 2) formed integrally to include a horizontal spring member f.sub.1 for pressing the drive pin e against the disk hub a of the magnetic disk, and a vertical spring portion f.sub.2 for biasing the drive pin e in one direction inside the drive hole d.
In this conventional arrangement using the spring member f having the two types of spring portions f.sub.1, f.sub.2 as integral parts thereof, the drive pin e is positioned in the drive hole d by the horizontal spring portion f.sub.1 and is retained at a fixed position within the drive hole d by the vertical spring portion f.sub.2. However, as illustrated in FIG. 2, the spring member f is formed to have an L-shaped configuration in which the horizontal spring portion f.sub.1 and vertical spring portion f.sub.2 intersect each other orthogonally at their end portions. The spring member f is attached to the spindle hub in such a manner that it is fixed at one end (i.e. the distal end of the horizontal spring portion f.sub.1) of the L-shaped body. Accordingly, when a pushing force produced at chucking acts upon the drive pin e fixedly secured to the other end (i.e. the distal end of the vertical spring member f.sub.2) of the L-shaped body, so-called torsional distortion or twisting occurs in the spring member f. In addition, when a fluctuation in reaction force with respect to the drive pin e occurs when the disk is driven into rotation, the spring member f undergoes compound deformation in both the horizontal and vertical directions, producing torsional distortion or twisting in the spring member f. Thus, with this prior-art expedient, the attitude of the drive pin e cannot be correctly maintained and, hence, the disk cannot be rotated reliably.
Furthermore, the spring member f is fabricated from a leaf spring and, for this reason, the biasing force on the drive pin e is set to be greater than necessary. Since the spring member f is fixed at one end to the spindle hub, moreover, an unnecessary force is applied to the spring member f if, say, the magnetic disk, having been loaded in the disk drive, is forcibly pulled off by hand inadvertently. This unnecessary force can damage or deform the spring member f or lead to other undesirable consequences.
The leaf spring mentioned above is formed from a flat spring member by punching work and therefore has burrs along its edges. If the portions with the burrs contact the underside of the spindle hub, which serves as a rotary body for chucking having the leaf spring attached thereto, the presence of the burrs detracts from the ability of the drive pin e to contact and follow up the edge of the drive hole d. As a result, the magnetic disk is rotated less reliably.
Moreover, since the spring member f is fixed at one end to the spindle hub, undesirable phenomena such as deformation of the spring member f occur when an unnecessary force is applied to the spring member at assembly or when the magnetic disk is loaded in the disk drive.